1. Field of the Invention
The invention relates to a process for the treatment of iron melts with a simultaneous increase of the scrap portion in the converter.
2. Description of the Prior Art
The treatment of iron melts by the addition of 25 to 30% by weight of scrap to the pig iron in the converter is known. The combustion heat from the oxidation of the carbon, manganese, silicon and other melts in the pig iron is sufficient to melt down a certain addition of scrap and to increase the temperature to a level which is required for steel melts.
However, in certain cases, it is desirable to increase the scrap portion to make the steel production capacity more flexible so that it can be adjusted to the prevailing market and production conditions. More particularly, it should be possible to process the scrap, which is available in excess and is more economical compared to pig iron.
Moreover, it is desirable to make the operation of the top-blowing oxygen converter less dependent on the pig iron supply, i.e., the effects of problems in the blast furnace operation on the steel production should be reduced.
The conventional oxygen injection technique allows an increase of the temperature of the bath in the converter only within very narrow limits. In addition, this measure results in high specific costs, since increased iron losses occur during after-blowing. Therefore, many attempts to improve the heat balance in the converter so that the addition of increased portions of scrap is possible.
Increasing the scrap portion by mixing of oxygen with fuel gas in special burners and, thus, increasing the heat balance of the converter is known. It is also known to melt down metals, such as, mixtures of scrap and pig iron, by means of a flame lance which is fed with hydrocarbons, wherein powdered solids, such as carbide, are introduced into the flame in order to improve the heat transfer (Austrian Pat. No. 313,942).
All these known processes have a common step in that, another fuel, possibly charged with an oxidizable solid, is added or supplied separately by means of a special nozzle to the oxygen jet after emerging from the lance.
It has also been suggested to add calcium carbide in lumps or pieces to the melt during the blowing procedure to simplify the process. Theoretically, the thermal energy obtained from the combustion of 1 kg of carbide should be sufficient to heat approximately 6 kg of iron from room temperature to a temperature of 1630.degree. C. However, in practice, this high efficiency which is required for an economical use of the carbide has not been achieved. Moreover, due to increased foaming of the slag, there are significant problems in the operation which by far outweigh any advantages.